Critical Speeds

In general, any rotating speed that is associated with high vibration amplitude. Often the rotor speeds, which correspond to natural frequencies of the system.

Condition Monitoring

Determining the condition of a machine by interpretation of measurements taken either periodically or continuously while the machine is running.

Clipping

A condition reached when the signal amplitude exceeds the limits of the amplifier or supply voltage. Signal peaks will be rounded or flattened resulting in inaccurate data.

Centerline Position

The average location, relative to the radial bearing centerline, of the shaft dynamic motion.

Center Frequency

For a bandpass filter, the center of the transmission band.

Choke (electronics)

A choke is an inductor designed to block (have a high reactance to) a particular frequency in an electrical circuit while passing signals of much lower frequency or direct current. Choke coils are inductances that isolate AC frequency currents from certain areas of a radio circuit. Chokes depend upon the property of self-inductance for their operation. They can be used to block alternating current while passing direct current (contrast with capacitor). Common-mode choke coils are useful in a wide range of prevention of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of electronic equipment. Types and construction - Chokes used in radio circuits are divided into two classes – those designed to be used with audio frequencies, and the others to be used with radio frequencies. Audio frequency coils, usually called A.F. chokes, can have ferromagnetic iron cores to increase their inductance. Chokes for higher frequencies (ferrite chokes or choke baluns) have ferrite cores. Chokes for even higher frequencies have air cores. Radio frequency coils, (R.F. chokes), usually don't have iron cores. In high power service so much heat would be produced in making and destroying the field in the core that the coil would burn up. Solid-state chokes - Solid-state chokes (SSC) can manage higher currents than traditional chokes. It reduces the high frequency buzzing noise when running under high electrical currents. Reference wikipedia

conservation of energy

The energy in a closed system cannot be changed but only interchanged, e.g. potential to kinetic energy.

contact stresses

The localized stress between contacting curved surfaces and between a curved and a flat surface, such as occurs in ball and roller bearings.

convection of beat

The transfer of heat from one part of a fluid to another due to ‘convection currents’ often due to gravity (natural convection) or by induced flow (forced convection).

convergent-divergent nozzle

A nozzle for fluid flow which decreases in area to a throat and then increases in area to the exit; the flow may be supersonicat outlet.